Sliding type variable resistor

ABSTRACT

A sliding type variable resistor having a resistance element and a conductive element mounted in parallel with each other on a dielectric base, a slider having a conductor on its lower surface, a guide rail for guiding the sliding movement of the slider, a housing covering the dielectric base for accommodating thereinside the slider and the guide rail, and an operating means fixed to the slider and projecting to the exterior through a slot in the upper wall of the housing. In the variable resistor, supporting pedestals are provided at longitudinal opposite end portions of the dielectric base for supporting the opposite ends of the guide rail thereby to ensure smooth and stable sliding movement of the slider.

United States Patent Sasaki et al. 1 June 20, 1972 [54] SLIDING TYPE VARIABLE RESISTOR [56] References Cited [72] Inventors: Nobuyuki Sasaki, Neyagawa; Shunzo Oka, UNITED STATES PATENTS Hrakaa; Yam, Osaka- 3,566,330 2 1971 lchikawa et al. ..338/l83 x Japan 2,706,230 4/1955 Bourns et al 3 Assignee; M hjt m -r Industrial c Ltd" 2,998,587 8/ l96l Bourns et al 338/183 Osaka, Japan Primary Examiner-Lewis H. Myers Flled! J 1971 Assistant Examiner-D. A. Tone [21] App] No 109 924 Attorney-Stevens, Davis, Miller & Mosher [57] ABSTRACT [30] Foreign Application Priority Data A sliding type variable resistor having a resistance element and a conductive element mounted in parallel with each other Jan. 30, 1970 Japan ..45/9923 on a dielectric base, a slider having a conductor on its lower Jan. 30, l970 Japan ..45/9924 surface, a guide rail for guiding the sliding movement of the Jan. 30, 1970 Japan ..45/9925 slider, a housing covering the dielectric base for accommodat- Jan. 30, 1970 Japan.... ..45/9926 ing thereinside the slider and the guide rail, and an operating Jan. 30, l970 Japan ..45/9927 means fixed to the slider and projecting to the exterior through a slot in the upper wall of the housing. In the variable resistor, supporting pedestals are provided at longitudinal op- [52] U.S. Cl ..338/183, 338/176 POSite nd portions f the dielectric base for Supporting the 5 Int Cl fl01 9/02 opposite ends of the guide rail thereby to ensure smooth and 58 Field of Search ....338/l76, 183 stable Sliding movement of the Slider- 6 Claims, 15 Drawing Figures PATENYEDJUH 20 I972 3. 671 .915

sum 5 or 8 FIG.8

PATENTEDJUH 20 1972 3.671.915

SHEET 7 OF 8 FIG. ll

O |24IO 4 10 SLIDING TYPE VARIABLE RESISTOR This invention relates to a sliding type variable resistor having improved means for supporting a guide rail and a slider for ensuring smooth and stable sliding movement of the slider within the resistor casing.

In prior art sliding type variable resistors of this kind, guide rails for guiding the sliding movement of a slider within the resistor casing have been supported in such a manner that the opposite end portions of the guide rails extendthrough holes bored in the opposite end walls of an outer housing and are fixed to the housing by locking means such as washers or springs or by caulking and like means. The prior art sliding type variable resistors having such supporting means have been defective in that a complex process isrequired for assembling same and a greater totallength of the resistance element than the housing is disadvantageous for application of the resistor in a set where there is little space.

Prior art sliding type variable resistors of the kind in which a single guide rail for guiding the sliding movement of a slider is disposed substantially centrally of the resistor casing have also been defective in that the slider tends to oscillate in the lateral direction.

It is therefore a primary object of the present invention to provide a novel and an improved sliding type variable resistor which is free from prior defects as above described.

The present invention provides a sliding type variable resistor, which is featured by the provision of a dielectric base having a resistance element and a conductive element mounted in parallel with each other on its upper surface, and supporting pedestals disposed at opposite end portions of the upper surface of the dielectric base. for supporting the opposite ends of one or a plurality of guide rails for guiding a slider which has a conductor fixed to its lower surface so that the slider can slide over the dielectric. base with its conductor in sliding contact with the resistance element and the conductive element while being ensured in its smooth and stable sliding movement by the guide rail or rails.

The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a partly sectional, side elevational view of a first embodiment of the present invention;

FIG. 2 is a sectional view taken on the line II II in FIG. 1;

FIG. 3 is a partly sectional, side elevational view of a second embodiment of the present invention;

FIG. 4 is a sectional view taken on the line IV IV in FIG.

FIG. 5 is an exploded view of the sistor shown in FIG. 3;

FIG. 6 is a perspective view of a third embodiment of the present invention;

FIG. 7 is an enlarged sectional view taken on the line VII VII in FIG. 6;

FIG. 8 is a sectional view taken on the line VIII VIII in FIG. 7;

FIG. 9 is a perspective view similar to FIG. 6, but showing the sliding type variable resistor, in a state in which its housing is removed;

FIG. 10 is an enlarged perspective view of a slider forming a part of the sliding type variable resistor shown in FIG. 6;

FIG. 11 is a sectional, side elevational view of a fourth embodiment of the present invention;

FIG. 12 is a perspective view of the sliding type variable resistor, shown in FIG. 11 in a state in which its housing is removed;

FIG. 13 is an enlarged perspective view of a slider and a sliding spring forming parts of the sliding type variable resistor, shown in FIG. 11;

FIG. 14 is a sectional, side elevational view of a fifth embodiment of the present invention; and

FIG. 15 is an enlarged sectional view taken on the line XV XV in FIG. 14. I

sliding type variable re- Referring to FIGS. 1 and 2, a first embodiment of the present invention includes a generally box-like housing I having a bottom opening and a plurality of dependant mounting legs 4. A longitudinal slot 2 is formed in the upper wall of the housing 1 so that an operating means fixed to a slider described later can extend through the slot 2. Mounting holes (not shown) are provided in the upper wall of the housing 1 adjacent to the opposite ends of the slot 2. The bottom opening of the housing 1 is closed by a dielectric base 3 of a moldable material which is fixed to the housing 1 by the mounting legs 4. Supporting pedestals 5 for supporting a guide rail, described later, extend upwardly from the longitudinal end portions of the dielectric base 3. A resistance element 6 and a conductive element 7 are mounted in parallel with each other on the upper surface of the dielectric base 3 between the supporting pedestals 5. The opposite ends of the resistance element 6 are securely fixed to the dielectric base 3 by external terminals 8. The opposite ends of the conductive element 7 are integral with terminal portions 9 and these terminal portions 9 are twisted to fix the conductive element 7 to the dielectric base 3. A semicircular recess I l is fonned at the top of each of the supporting pedestals 5 extending from the opposite end portions of the dielectric base 3, and a guide rail 10 is received at opposite ends in these semicircular recesses 11. A slider 13 of electrically insulating material is slidably mounted onthe guide rail 10 with a channel 12 formed at the center of the lower surface thereof engaging the guide rail 10. A sliding spring 14 is fixed to the upper surface of the slider 13 and engages the inside surface of the upper wall of the housing 1 so as to prevent upward floating of the guide rail 10 off the supporting pedestals 5. A conductor 15 of electrically conductive resilient material is fixed to the lower surface of the slider 13 slidably engaging the guide rail 10 within the space between the housing 1 and the dielectric base 3. The conductor 15 is provided with fingers at one end. One of the fingers makes a positive engagement with the surface of the resistance element 6 by its resiliency, while the other finger makes a positive engagement with the surface of the conductive element 7 by its resiliency also. Thus, the conductor 15 is moved in integral relation with the slider 13 while engaging at its fingers with the resistance element 6 and the conductive element 7. An operating means 16 is fixed to the upper surface of the slider 13 and extends upwardly through the slot 2 fonned in the upper wall of the housing 1 so that, when the operating means 16 is manipulated by hand, the slider 13 makes a sliding movement by being guided by the guide rail 10.

In assembling the sliding type variable resistor, the guide rail 10 is placed to span between the supporting pedestals 5 provided at the opposite end portions of the dielectric base 3, and then the slider 13 is mounted on the guide rail 10 in such a manner that the channel 12 formed at the lower surface of the slider 13 to engage with the guide rail 10. After fixing the sliding spring 14 to the upper surface of the slider 13, the housing 1 is fitted on the dielectric base 3 in such a manner that the operating means 16 protrudes from the slot 2, and the dielectric base 3 is fixed in the bottom opening of the housing I by bending inwardly the mounting legs 4 extending from the end edges of the bottom opening of the housing 1. When the housing 1 and the dielectric base 3 are fixed together in this manner, the guide rail 10 is securely supported between the slider 13 and the supporting pedestals 5 by the action of the sliding spring 14 disposed between the inside surface of the upper wall of the housing 1 and the upper surface of the slider 13. Although only one guide rail 10 is shown herein, two or more guide rails may be provided as required. In this case, the number of supporting pedestals 5 may be correspondingly increased to meet the number of the guide rails 10.

The sliding type variable resistor having a structure as above described has various advantages over prior art variable resistors of this type. Parts to be incorporated in a miniature set or a set having a narrow space therein have a limited size and any extra length, even if it is very slight, is objectionable. In contrast with the prior art variable resistor of this type in which the guide rail is fixed at the outside of the housing, the present invention is advantageous in that the size of the variable resistor can be considerably reduced compared with the prior art variable resistor, since the guide rail is fixed within the resistor casing. Another advantage of the present invention resides in the fact that the variable resistor can be very easily assembled because the sliding spring disposed between the upper surface of the slider and the inside surface of the upper wall of the housing is utilized to fixedly support the guide rail between the lower surface of the slider and the supporting pedestals which are integral with the dielectric base. Thus, the variable resistor according to the present invention has a simple structure and can be manufactured at low cost.

Referring to FIGS. 3, 4 and 5, a second embodiment of the present invention includes a generally box-like housing 101 having a bottom opening and a plurality of dependant mounting legs 106. A longitudinal slot 102 is formed in the upper wall of the housing 101 so that an operating means described later can protrude from the slot 102. A pair of mounting holes 103 are provided in the upper wall of the housing 101 adjacent to the opposite ends of the slot 102. Portions of the opposite end walls of the housing 101 are cut open and bent inwardly to form a plurality of inwardly extending lugs 104. The bottom opening of the housing 101 is closed by a dielectric base 105 of moldable material which is fixed to the housing 101 by bending inwardly the mounting legs 106. Supporting pedestals 107 for supporting a guide rail described later extend upwardly from the longitudinal end portions of the dielectric base 105. A resistance element 108 and a conductive element 109 are mounted in parallel with each other on the upper surface of the dielectric base 105 between the supporting pedestals 107. The opposite ends of the resistance element 108 are securely fixed to the dielectric base 105 by external terminals 110. The opposite ends of the conductive element 109 are integral with terminal portions 111 and these terminal portions 111 are twisted to fix the conductive element 109 to the dielectric base 105. A semicircular recess 113 is formed at the opposite end portions of the dielectric base 105, and a guide rail 112 is received at opposite ends in these semicircu lar recesses 113. A slider 115 of electrically insulating material is slidably mounted on the guide rail 1 12 with a channel 114 formed at the center of the lower surface thereof engaging the guide rail 112. The lugs 104 extending inwardly from the opposite end walls of the housing 101 engage the upper surface of the opposite end portions of the guide rail 112 so as to prevent upward floating of the guide rail 112 ofi the supporting pedestals 107. A conductor 116 of electrically conductive resilient material is fixed to the lower surface of the slider 115 slidably engaging the guide rail 112 within the space between the housing 101 and the dielectric base 105. The conductor 116 is provided with fingers at one end. One of the fingers makes positive engagement with the surface of the resistance element 108 by its resiliency, while the other finger makes positive engagement with the surface of the conductive element 109 also by its resiliency. Thus, the conductor 116 is moved in integral relation with the slider 115 while engaging at its fingers with the resistance element 108 and the conductive element 109. An operating means 117 is fixed to the upper surface of the slider 1 15 and extends upwardly through the slot 102 formed in the upper wall of the housing 101 so that, when the operating means 117 is manipulated by hand, the slider 115 makes a sliding movement by being guided by the guide rail 112.

According to the present embodiment, the guide rail 112 is securely supported in place by being held between the supporting pedestals 107 and the inwardly extending lugs 104 which are formed by cutting open portions of the opposite end walls of the housing 101 and bending these portions inwardly. A guide member of any suitable shape may be employed in lieu of the guide rail 112 described hereinbefore. Although only one guide rail 112 is shown herein, two or more guide rails may be provided as required. In this case, the number of the supporting pedestals 107 and the lugs 104 may be correspondingly increased to meet the number of the guide rails 112.

Referring to FIGS. 6 through 10, a third embodiment of the present invention includes a dielectric base 201 of electrically insulating material. On the upper surface of the dielectric base 201, resistance element 202 and a conductive element 203 are mounted in parallel with each other in the longitudinal direction of the dielectric base 201. A pair of parallel ridges 204 and 204' extend upwardly from the upper surface portions adjacent to the longitudinal side edges of the dielectric base 201 as an integral part thereof, and the opposite end portions of these ridges 204 and 204 are raised to form two pairs of spaced guide rail supporting pedestals 205 and 205' respectively. The opposite ends of the resistance element 202 are securely fixed to the dielectric base 201 by external terminals 4 206. The opposite ends of the conductive element 203 are integral with terminal portions 207 and these terminal portions 207 are twisted to fix the conductive element 203 to the dielectric base 201. A plurality of cutouts 208 and 208' (208 not shown) are formed on the longitudinal side surfaces of the dielectric base 201. A generally box-like housing 209 has a bottom opening, and a plurality of mounting legs 210 and 210 extend from the lower end of the longitudinal side walls thereof. The mounting legs 210 and 210' are fitted in the eutouts 208 and 208' of the dielectric base 201 and are then bent inwardly to firmly engage the bottom surface of the dielectric base 201 so as to securely fix the dielectric base 201 in the bottom opening of the housing 209. A longitudinal slot 211 is formed in the upper wall of the housing 209, and a pair of mounting holes 212 are provided in the upper wall of the housing 209 adjacent to the opposite ends of the slot 21 1 so as to mount the resistor in a set (not shown). Portions adjacent to the ends of the longitudinal side walls of the housing 209 are cut open and bent inwardly to form two pairs of inwardly ex tending lugs 213 and 213' which are slightly spaced from the guide rail supporting pedestals 205 and 205 integrally formed on the dielectric base 201. A slider 214 of plastic material is slidably disposed within the space between the housing 209 and the dielectric base 201 and is formed with a pair of semicircular channels 215 and 215' on its opposite side surfaces. The slider 214 is slidably engaged by two guide rails 216 and 216 at its semicircular channels 215 and 215 respectively. The guide rails 216 and 216' are supported at opposite ends, on the respective pairs of the guide rail supporting pedestals 205 and 205' and are engaged at their upper surface portions by the respective pairs of the inwardly extending lugs 213 and 213 formed adjacent to the four comers of the housing 209. That is, the opposite ends of the two guide rails 216 and 216' are fixed in place by being held between the respective pairs of the guide rail supporting pedestals 205 and 205' integral with the dielectric base 201 and the respective pairs of the inwardly extending lugs 213 and 213' formed adjacent to the four corners of the housing 209. An operating means 217 of metal material is fixed to the upper surface of the slider 214 and protrudes from the slot 211 formed in the upper wall of the housing 209 so that, when the operating means 217 is manipulated by hand, the slider 217 makes a sliding movement by being guided by the guide rails 216 and 216'. A plurality of dowels 220 are provided on the bottom surface of the slider 217, and a conductor 218 and a contactor 219 in the form of a resilient metal stn'p are fixed to the bottom surface of the slider 217 by crushing the heads of the dowels 220. The conductor 218 and the contactor 219 make positive engagement with the resistance element 202 and the conductive element 203 are respectively mounted on the dielectric base 201 due to their own resiliency. Manipulation of the operating means 217 causes sliding movement of the slider 214 along the guide rails 216 and 216' so that the conductor 218 and the contactor 219 carried by the slider 214 make a sliding movement while contacting the resistance element 202 and the condutive element 203 respectively. The four corners of the slider 214 are cut out as at 221 and 221' so that the sliding movement of the slider 214 may not be obstructed by the supporting pedestals 205 and 205.

In assembling the sliding type variable resistor, the guide rails 216 and 216' are mounted in the respective semicircular channels 215 and 215' formed on the opposite side surfaces of the slider 214, and then the slider 214 carrying these elements is put into the housing 209 in such a manner that the operating means 217 fixed to the upper surface thereof protrudes from the slot 211 of the housing 209, and the opposite ends of the guide rails 216 and 216 engage the respective pairs of the inwardly extending lugs 213 and 213' formed adjacent to the four corners of the housing 209. Then, the dielectric base 201 is positioned in the bottom opening of the housing 209, and after fitting the mounting legs 210 and 210 in the respective cutouts 208 and 208' of the dielectric base 201, the mounting legs 210 and 210' are bent inwardly to firmly engage the bottom surface of the dielectric base 201 so as to fix the dielectric base 201 in the bottom opening of the housing 209. When the dielectric base 201 is thus fixed to the housing 209, the guide rails 216 and 216' are fixed in place by being held between the respective pairs of the guide rail supporting pedestals 205 and 205" integral with the dielectric base 201 and the respective pairs of the inwardly extending lugs 213 and 213' formed adjacent to the four comers of the housing 209.

In the sliding type variable resistor assembled in this manner, lateral oscillatory movement of the operating means 217 and the slider 214 due to lateral force imparted to the operating means 217 can be reduced to a minimum by virtue of the fact that the slider 214 is held between the two guide rails 216 and 216' which are fixed in place by the inwardly extending lugs 213 and 213' and the guide rail supporting pedestals 205 and 205' as above described. Further, the ridges 204 and 204' standing up from the upper surface portions adjacent to the opposite side edges of the dielectric base 209 are sufficiently spaced from the slider 214 so that they may not be in contact with the slider 214 during the sliding movement of the slider 214, but only when an unusual force is imparted to the slider 214 from above, as when a knob (not shown) is press-fitted on the driving lever 217, the ridges 204 and 204' bear against the slider 214 so as to prevent undesirable deformation of the guide rails 216 and 216'.

The sliding type variable resistor having a structure as above described is advantageous in many points. In the first place, the structure in which the slider is firmly but slidably held between the two stationary guide rails provides the advantage that undesirable lateral oscillatory movement of the slider can be very easily prevented and the required dimensional precision can be very easily obtained compared with the prior art structure in which the prevention of lateral oscillating movements of the slider is dependent upon the dimensions of the housing and dielectric base. In the second place, the use of the two guide rails for slidably holding the slider therebetween is advantageous in that lateral and vertical oscillating movement of the slider can be reduced to a minimum so that the slider can make a very smooth and stable sliding movement without oscillating in its direction of travel.

A fourth embodiment of the present invention which will now be described is substantially similar in structure to the third embodiment described above and only differs from the latter in minor details. Referring to FIGS. 11, 12 and 13, a slider 314 is provided with a generally rectangular recess 318 on its upper surface and an operating means 317 is fixed to the center of the recess 318. The slider 314 is provided on its opposite side surfaces with a pair of semicircular channels 315 and 315' which communicate with the recess 318 through respective cutouts 319 and 319'. A sliding spring 320 of metal material having a shape as best shown in FIG. 13 is fitted in the recess 318 on the upper surface of the slider 314 and has a 70 central opening 321 through which the operating means 317 can extend upwardly. Spring portions 322 and 322 extending obliquely upwardly from the opposite edges of the central opening 321 of the sliding spring 320 are in pressure contact extend obliquely downwardly from the opposite side surfaces of the sliding spring 320 for sliding contact at their ends with respective guide rails 316 and 316. The operating means 317 is electrically connected to a housing 309 through the sliding spring 320 and the guide rails 316 and 316'. The pressure encountered by the slider 314 during its sliding movement due to the manipulation of the operating means 317 can be set at any suitable value by suitably adjusting the pressure with which the tongues 323 and 323' of the sliding spring 320 engage the respective guide rails 316 and 316.

The sliding type variable resistor of the above structure in which the operating means is electrically connected to the housing through the sliding spring and guide rails is especially used to advantage in an amplifier 'of high sensitivity in that generation of undesirable noises such as an induced hum can be effectively avoided, even when the operating means is touched by a part of the human body, because the operating means is electrically connected to the housing which is grounded. A further advantage of this sliding type variable resistor, in which the pressure encountered by the slider during its sliding movement is controlled by the pressure with which the tongues of the sliding spring engage the guide rails, resides in the fact that the difierent sense of resistance against the same sliding movement of the slider due to a variation in the ambient temperature can be substantially eliminated unlike the prior manner of controlling such pressure by a layer of grease.

Referring to FIGS. 14 and 15, a fifth embodiment of the present invention includes a dielectric base 401 of electrically insulating material. A resistance element 402 and a conductive element 403 are mounted in parallel with each other on the upper surface of the dielectric base 401 in the longitudinal direction thereof. A pair of parallel ridges 404 and 404' extendupwardly from the upper surface portions adjacent to the longitudinal side edges of the dielectric base 401 as an integral part thereof, and the opposite end portions of these ridges 404 and 404' are raised to form two pairs of spaced guide rail supporting pedestals 405 and 405' respectively. The opposite ends of the resistance element 402 are securely fixed to the dielectric base 401 by external terminals 406. The opposite ends of the conductive element 403 are integral with terminal portions 407 and these terminal portions 407 are twisted to fix the conductive element 403 to the dielectric base 401. A plurality of cutouts (not shown) are formed on the longitudinal side surfaces of the dielectric base 401. A generally box-like housing 408 has a bottom opening, and a plurality of mounting legs 409 and 409' extend from the lower end of the longitudinal side walls thereof. The mounting legs 409 and 409 are fitted in the cutouts of the dielectric base 401 and are then bent inwardly to firmly engage the bottom surface of the dielectric base 401 so as to securely fix the dielectric base 401 in the bottom opening of the housing 408. A longitudinal slot 410 is formed in the upper wall of the housing 408, and a pair of mounting holes (not shown) are provided in the upper wall of the housing 408 adjacent to the opposite ends of the slot 410 so as to mount the resistor in a set (not shown). A slider 411 of plastic material is slidably disposed within the space 0 between the housing 408 and the dielectric base 401 and is fomred with a pair of semicircular channels 412 and 412' on its opposite side surfaces. The slider 411 is slidably engaged by two guide rails 413 and 413' at its semicircular channels 412 and 412' respectively. The guide rails 413 and 413' are supported at opposite ends on the respective pairs of the guide rail supporting pedestals 405 and 405'. An operating means 414 is fixed to the upper surface of the slider 411 and extends upwardly through the slot 410 formed in the upper wall of the housing 408. A sliding spring 415 is disposed between the upper surface of the slider 411 and the inside surface of the upper wall of the housing 408. The sliding spring 415 has a central opening and a pair of tabs 416 and 416' extending towards each other from the opposite edges of the central opening. After the sliding spring 415 is fitted on the operating with the operating means 317. Apair of tongues 323 and 323' means 414, the tabs 416 and 416' are pressed against the operating means 414 to securely fix the sliding spring 415 to the upper surface of the slider 411. Due to the provision of the sliding spring 415, the slider 411 is forced downwards by the resiliency of the spring 415 so that the guide rails 413 and 413' can be fixedly positioned on the guide rail supporting pedestals 405 and 405 without floating upwardly away from the supporting pedestals 405 and 405'. Thus, when the operating means 414 protruding from the slot 410 formed in the upper wall of the housing 408 is manipulated by hand, the slider 411 makes a sliding movement by being guided by the guide rails 413 and 413. A conductor 417 and a contactor 418 in the form of a resilient metal strip are fixed to the bottom surface of the slider 411. The conductor 417 and the contactor 418 make positive engagement with the resistance element 402 and the contact plate 403 respectively mounted on the dielectric base 401 due to their own resiliency. Manipulation of the operating means 414 causes sliding movement of the slider 411 along the guide rails 413 and 413' so that the conductor 417 and the contactor 418 carried by the slider 41 1 make a sliding movement while contacting the resistance element 402 and the contact plate 403 respectively.

In assembling, the sliding spring 415 is fixed to the upper surface of the slider 411, and the conductor 417 and the contactor 418 are fixed to the lower surface of the slider 41 l. The guide rails 413 and 413' are mounted in the respective semicircular channels 412 and 412 formed on the opposite side surfaces of the slider 411, and then the slider 411 carrying these elements is put into the housing 408 in such a manner that the operating means 414, fixed to the upper surface thereof, protrudes from the slot 410 of the housing 408. Then, the dielectric base 401 is positioned in the bottom opening of the housing 408, and after fitting the mounting legs 409 and 409' in the cutouts of the dielectric base 401, the mounting legs 409 and 409' are bent inwardly to firmly engage the bottom surface of the dielectric base 401 so as to fix the dielectric base 401 in the bottom opening of the housing 408. When the dielectric base 401 is thus fixed to the housing 408, the guide rails 413 and 413 received in the semicircular channels 412 and 412' formed on the opposite side surfaces of the slider 411 are fixed at their opposite ends on the respective pairs of the guide rail supporting pedestals 405 and 405' provided on the dielectric base 401 by the action of the sliding spring 415.

The sliding type variable resistor having a structure as above described is advantageous in that lateral and vertical oscillating movement of the slider can be reduced to a minimum so that the slider can make very smooth and stable sliding movement without oscillating in its direction of travel because the slider is firmly but slidably held between the two guide rails.

What is claimed is:

1. A sliding type variable resistor comprising a dielectric base mounting a resistance element and a conductive element thereon and provided with guide rail supporting means adjacent to the longitudinal opposite ends thereof, a slider, a conductor of electrically conductive resilient material fixed to the lower surface of said slider for sliding contact with the surface of said resistance element and said conductive element, an operating means fixed to the upper surface of said slider, at least one guide rail fixedly supported at its opposite ends by said guide rail supporting means for guiding the sliding movement of said slider, a housing of metal material fixed to said dielectric base to cover the upper surface of said dielectric base for accommodating there inside said slider, said guide rail supporting means and said guide rail, and means provided inside of said housing for holding said guide rail in place with respect to said guide rail supporting means, said housing havconductor of electrically conductive resilient material fixed to the lower surface of sat slider for sliding contact with the surface of said resistance element and said conductive element an operating means fixed to the upper surface of said slider, at least one guide rail fixedly supported at its opposite ends by said guide rail supporting means for guiding the sliding movement of said slider, a housing of metal material fixed to said dielectric base to cover the upper surface of said dielectric base for accommodating there inside said slider, said guide rail supporting means and said guide rail, and a sliding spring disposed between the upper surface of said slider and the inside surface of the upper wall of said housing so as to slidably hold said slider between the upper wall of said housing and said guide rail, said housing having an elongated slot in its upper wall so that said operating means fixed to said slider can protrude to the exterior from said slot.

3. A sliding type variable resistor comprising a dielectric base mounting a resistance element and a conductive element thereon and provided with guide rail supporting means adjacent to the longitudinal opposite ends thereof, a slider, a conductor of electrically conductive resilient material fixed to the lower surface of said slider for sliding contact with the surface of said resistance element and said conductive element, an operating means fixed to the upper surface of said slider, at least one guide rail fixedly supported at its opposite ends by said guide rail supporting means for guiding the sliding movement of said slider, a housing of metal material fixed to said dielectric base to cover the upper surface of said dielectric base for accommodating there inside said slider, said guide rail supporu'ng means and said guide rail, said housing being provided with lugs extending inwardly from the side walls adjacent to said guide rail supporting means for engaging the opposite ends of said guide rail from above thereby to press said guide rail against said guide rail supporting means to firmly fix said guide rail in place, said housing having an elongated slot in its upper wall so that said operating means fixed to said slider can protrude to the exterior from said slot.

4. A sliding type variable resistor as claimed in claim 3, in which said guide rail is provided along each side surface of said slider, and said housing is provided with lugs extending inwardly from the side walls adjacent to said guide rail supporting means for engaging the opposite ends of these two guide rails from above, thereby to press said guide rails against said guide rail supporting means to firmly fix said guide rails in place,

5. A sliding type variable resistor as claimed in claim 3, in which a sliding spring having outwardly extending tongues engaging said guide rails is fitted on the lower end portion of said operating means so as to establish pressure engagement between said guide rails and said slider for ensuring smooth and stable sliding movement of said slider along said guide rails.

6. A sliding type variable resistor as claimed in claim 2, in which said guide rail is provided along each side surface of said slider, and a sliding spring is fixed to the upper surface of said slider so that it makes pressure engagement with the inside surface of the upper wall of said housing. 

1. A sliding type variable resistor comprising a dielectric base mounting a resistance element and a conductive element thereon and provided with guide rail supporting means adjacent to the longitudinal opposite ends thereof, a slider, a conductor of electrically conductive resilient material fixed to the lower surface of said slider for sliding contact with the surface of said resistance element and said conductive element, an operating means fixed to the upper surface of said slider, at least one guide rail fixedly supported at its opposite ends by said guide rail supporting means for guiding the sliding movement of said slider, a housing of metal material fixed to said dielectric base to cover the upper surface of said dielectric base for accommodating there inside said slider, said guide rail supporting means and said guide rail, and means provided inside of said housing for holding said guide rail in place with respect to said guide rail supporting means, said housing having an elongated slot in its upper wall so that said operating means fixed to said slider can protrude to the exterior from said slot.
 2. A sliding type variable resistor comprising a dielectric base mounting a resistance element and a conductive element thereon and provided with guide rail supporting means adjacent to the longitudinal opposite ends thereof, a slider, a conductor of electrically conductive resilient material fIxed to the lower surface of said slider for sliding contact with the surface of said resistance element and said conductive element an operating means fixed to the upper surface of said slider, at least one guide rail fixedly supported at its opposite ends by said guide rail supporting means for guiding the sliding movement of said slider, a housing of metal material fixed to said dielectric base to cover the upper surface of said dielectric base for accommodating there inside said slider, said guide rail supporting means and said guide rail, and a sliding spring disposed between the upper surface of said slider and the inside surface of the upper wall of said housing so as to slidably hold said slider between the upper wall of said housing and said guide rail, said housing having an elongated slot in its upper wall so that said operating means fixed to said slider can protrude to the exterior from said slot.
 3. A sliding type variable resistor comprising a dielectric base mounting a resistance element and a conductive element thereon and provided with guide rail supporting means adjacent to the longitudinal opposite ends thereof, a slider, a conductor of electrically conductive resilient material fixed to the lower surface of said slider for sliding contact with the surface of said resistance element and said conductive element, an operating means fixed to the upper surface of said slider, at least one guide rail fixedly supported at its opposite ends by said guide rail supporting means for guiding the sliding movement of said slider, a housing of metal material fixed to said dielectric base to cover the upper surface of said dielectric base for accommodating there inside said slider, said guide rail supporting means and said guide rail, said housing being provided with lugs extending inwardly from the side walls adjacent to said guide rail supporting means for engaging the opposite ends of said guide rail from above thereby to press said guide rail against said guide rail supporting means to firmly fix said guide rail in place, said housing having an elongated slot in its upper wall so that said operating means fixed to said slider can protrude to the exterior from said slot.
 4. A sliding type variable resistor as claimed in claim 3, in which said guide rail is provided along each side surface of said slider, and said housing is provided with lugs extending inwardly from the side walls adjacent to said guide rail supporting means for engaging the opposite ends of these two guide rails from above, thereby to press said guide rails against said guide rail supporting means to firmly fix said guide rails in place.
 5. A sliding type variable resistor as claimed in claim 3, in which a sliding spring having outwardly extending tongues engaging said guide rails is fitted on the lower end portion of said operating means so as to establish pressure engagement between said guide rails and said slider for ensuring smooth and stable sliding movement of said slider along said guide rails.
 6. A sliding type variable resistor as claimed in claim 2, in which said guide rail is provided along each side surface of said slider, and a sliding spring is fixed to the upper surface of said slider so that it makes pressure engagement with the inside surface of the upper wall of said housing. 